Re: [PATCH v5 3/7] qapi/commands: Optionally generate trace for QMP commands

[Markus Armbruster]

Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:

> Add trace generation disabled by default and new option --gen-trace to
> enable it.  The next commit will enable it for qapi/, but not for qga/
> and tests/.  Making it work for the latter two would involve some Meson
> hackery to ensure we generate the trace-events files before trace-tool
> uses them.  Since we don't actually support tracing there, we'll bypass
> that problem.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  scripts/qapi/commands.py | 91 +++++++++++++++++++++++++++++++++++-----
>  scripts/qapi/main.py     | 10 +++--
>  2 files changed, 87 insertions(+), 14 deletions(-)
>
> diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
> index 17e5ed2414..0c171cb880 100644
> --- a/scripts/qapi/commands.py
> +++ b/scripts/qapi/commands.py
> @@ -53,7 +53,8 @@ def gen_command_decl(name: str,
>  def gen_call(name: str,
>               arg_type: Optional[QAPISchemaObjectType],
>               boxed: bool,
> -             ret_type: Optional[QAPISchemaType]) -> str:
> +             ret_type: Optional[QAPISchemaType],
> +             gen_trace_events: bool) -> str:
>      ret = ''
>  
>      argstr = ''
> @@ -71,14 +72,37 @@ def gen_call(name: str,
>      if ret_type:
>          lhs = 'retval = '
>  
> -    ret = mcgen('''
> +    name = c_name(name)
> +    upper = name.upper()
>  
> -    %(lhs)sqmp_%(c_name)s(%(args)s&err);
> +    if gen_trace_events:
> +        ret += mcgen('''
> +
> +    if (trace_event_get_state_backends(TRACE_QMP_ENTER_%(upper)s)) {
> +        g_autoptr(GString) req_json = qobject_to_json(QOBJECT(args));
> +
> +        trace_qmp_enter_%(name)s(req_json->str);
> +    }
> +    ''',
> +                     upper=upper, name=name)
> +
> +    ret += mcgen('''
> +
> +    %(lhs)sqmp_%(name)s(%(args)s&err);
>  ''',
> -                c_name=c_name(name), args=argstr, lhs=lhs)
> +                 name=name, args=argstr, lhs=lhs)
>  
>      ret += mcgen('''
>      if (err) {
> +''')
> +
> +    if gen_trace_events:
> +        ret += mcgen('''
> +        trace_qmp_exit_%(name)s(error_get_pretty(err), false);
> +''',
> +                     name=name)
> +
> +    ret += mcgen('''
>          error_propagate(errp, err);
>          goto out;
>      }
> @@ -90,6 +114,25 @@ def gen_call(name: str,
>      qmp_marshal_output_%(c_name)s(retval, ret, errp);
>  ''',
>                       c_name=ret_type.c_name())
> +
> +    if gen_trace_events:
> +        if ret_type:
> +            ret += mcgen('''
> +
> +    if (trace_event_get_state_backends(TRACE_QMP_EXIT_%(upper)s)) {
> +        g_autoptr(GString) ret_json = qobject_to_json(*ret);
> +
> +        trace_qmp_exit_%(name)s(ret_json->str, true);
> +    }
> +    ''',
> +                         upper=upper, name=name)
> +        else:
> +            ret += mcgen('''
> +
> +    trace_qmp_exit_%(name)s("{}", true);
> +    ''',
> +                         name=name)
> +
>      return ret
>  
>  
> @@ -126,10 +169,19 @@ def gen_marshal_decl(name: str) -> str:
>                   proto=build_marshal_proto(name))
>  
>  
> +def gen_trace(name: str) -> str:
> +    return mcgen('''
> +qmp_enter_%(name)s(const char *json) "%%s"
> +qmp_exit_%(name)s(const char *result, bool succeeded) "%%s %%d"
> +''',
> +                 name=c_name(name))
> +
> +
>  def gen_marshal(name: str,
>                  arg_type: Optional[QAPISchemaObjectType],
>                  boxed: bool,
> -                ret_type: Optional[QAPISchemaType]) -> str:
> +                ret_type: Optional[QAPISchemaType],
> +                gen_trace_events: bool) -> str:
>      have_args = boxed or (arg_type and not arg_type.is_empty())
>      if have_args:
>          assert arg_type is not None
> @@ -184,7 +236,7 @@ def gen_marshal(name: str,
>      }
>  ''')
>  
> -    ret += gen_call(name, arg_type, boxed, ret_type)
> +    ret += gen_call(name, arg_type, boxed, ret_type, gen_trace_events)
>  
>      ret += mcgen('''
>  
> @@ -242,11 +294,13 @@ def gen_register_command(name: str,
>  
>  
>  class QAPISchemaGenCommandVisitor(QAPISchemaModularCVisitor):
> -    def __init__(self, prefix: str):
> +    def __init__(self, prefix: str, gen_trace_events: bool):
>          super().__init__(
>              prefix, 'qapi-commands',
> -            ' * Schema-defined QAPI/QMP commands', None, __doc__)
> +            ' * Schema-defined QAPI/QMP commands', None, __doc__,
> +            gen_trace_events=gen_trace_events)
>          self._visited_ret_types: Dict[QAPIGenC, Set[QAPISchemaType]] = {}
> +        self._gen_trace_events = gen_trace_events
>  
>      def _begin_user_module(self, name: str) -> None:
>          self._visited_ret_types[self._genc] = set()
> @@ -265,6 +319,17 @@ def _begin_user_module(self, name: str) -> None:
>  
>  ''',
>                               commands=commands, visit=visit))
> +
> +        if self._gen_trace_events and commands != 'qapi-commands':
> +            self._genc.add(mcgen('''
> +#include "trace/trace-qapi.h"
> +#include "qapi/qmp/qjson.h"
> +#include "trace/trace-%(nm)s_trace_events.h"
> +''',
> +                                 nm=c_name(commands, protect=False)))
> +            # We use c_name(commands, protect=False) to turn '-' into '_', to
> +            # match .underscorify() in trace/meson.build
> +
>          self._genh.add(mcgen('''
>  #include "%(types)s.h"
>  
> @@ -326,7 +391,10 @@ def visit_command(self,
>          with ifcontext(ifcond, self._genh, self._genc):
>              self._genh.add(gen_command_decl(name, arg_type, boxed, ret_type))
>              self._genh.add(gen_marshal_decl(name))
> -            self._genc.add(gen_marshal(name, arg_type, boxed, ret_type))
> +            self._genc.add(gen_marshal(name, arg_type, boxed, ret_type,
> +                                       self._gen_trace_events))
> +            if self._gen_trace_events:
> +                self._gent.add(gen_trace(name))
>          with self._temp_module('./init'):
>              with ifcontext(ifcond, self._genh, self._genc):
>                  self._genc.add(gen_register_command(
> @@ -336,7 +404,8 @@ def visit_command(self,
>  
>  def gen_commands(schema: QAPISchema,
>                   output_dir: str,
> -                 prefix: str) -> None:
> -    vis = QAPISchemaGenCommandVisitor(prefix)
> +                 prefix: str,
> +                 gen_trace_events: bool) -> None:
> +    vis = QAPISchemaGenCommandVisitor(prefix, gen_trace_events)
>      schema.visit(vis)
>      vis.write(output_dir)
> diff --git a/scripts/qapi/main.py b/scripts/qapi/main.py
> index f2ea6e0ce4..ecff41910c 100644
> --- a/scripts/qapi/main.py
> +++ b/scripts/qapi/main.py
> @@ -32,7 +32,8 @@ def generate(schema_file: str,
>               output_dir: str,
>               prefix: str,
>               unmask: bool = False,
> -             builtins: bool = False) -> None:
> +             builtins: bool = False,
> +             gen_trace_events: bool = False) -> None:
>      """
>      Generate C code for the given schema into the target directory.
>  
> @@ -49,7 +50,7 @@ def generate(schema_file: str,
>      schema = QAPISchema(schema_file)
>      gen_types(schema, output_dir, prefix, builtins)
>      gen_visit(schema, output_dir, prefix, builtins)
> -    gen_commands(schema, output_dir, prefix)
> +    gen_commands(schema, output_dir, prefix, gen_trace_events)
>      gen_events(schema, output_dir, prefix)
>      gen_introspect(schema, output_dir, prefix, unmask)
>  
> @@ -74,6 +75,8 @@ def main() -> int:
>      parser.add_argument('-u', '--unmask-non-abi-names', action='store_true',
>                          dest='unmask',
>                          help="expose non-ABI names in introspection")

Let's add

       # Option --gen-trace exists so we can avoid solving build system
       # problems.  TODO Drop it when we no longer need it.

> +    parser.add_argument('--gen-trace', action='store_true',
> +                        help="add trace events to qmp marshals")
>      parser.add_argument('schema', action='store')
>      args = parser.parse_args()
>  
> @@ -88,7 +91,8 @@ def main() -> int:
>                   output_dir=args.output_dir,
>                   prefix=args.prefix,
>                   unmask=args.unmask,
> -                 builtins=args.builtins)
> +                 builtins=args.builtins,
> +                 gen_trace_events=args.gen_trace)
>      except QAPIError as err:
>          print(f"{sys.argv[0]}: {str(err)}", file=sys.stderr)
>          return 1